Ocular cutter with enhanced cutting action

ABSTRACT

The inner needle in a guillotine type ocular cutter is ground and placed within the swaged outer needle in an interference fit, so that a radial force is exerted by said inner needle on said outer needle to better shear the ocular tissue. Further, a positive stop is effected on the drive shaft controlling the inner needle so that the distance from the end of the outer needle port to the tissue is minimized. Alternately, the drive shaft has a dwell exerted on it.

FIELD OF THE INVENTION

The invention relates generally to the field of tissue removal. Morespecifically, the invention relates to ocular cutters for tissueremoval. Most specifically, the invention relates to ocular cutters fortissue removal where the ocular cutter has enhanced cutting action.

BACKGROUND OF THE INVENTION

In recent years, tissue removal devices have become quite commonplace.Generally, in the field of ocular surgery, tissue removal devices havebeen found in the form of phacoemulsification devices, as well as ocularcutters. In an ocular cutter, there has generally been found a doubleneedle configuration where an outer chamber or "needle" is concentricwith an inner "needle". In the outer needle there is an open port, andthe inner needle reciprocates within that open port. Tissue is suckedinto the port of the outer needle by vacuum pressure within the innerchamber. When the inner needle reciprocates past the open port, thetissue is sheared. The tissue is then removed down the length of theinner needle by suction.

While these "guillotine" type ocular cutters have been successfulinstruments, they have posed certain drawbacks. First, there has alwaysbeen an incentive to provide for the most precise cutting mechanism. Themore precise the cutter is, the less chance of tissue trauma. The riskof improper amounts of tissue, or cutting the improper size of thetissue, is also reduced. Frequently, however there is incomplete shearof tissue at the outer needle port.

Second, because the port of the outer needle generally is designed at adistance from the end of the outer needle, present ocular cutters allhave a certain minimum width of tissue from the point of contact withthe ocular cutter which can not be cut. When cutting takes place, thereis always this tolerance which must be taken into account beforecutting. Thus, the cutting approach may not be applicable for small,precise cuts which require cutting at the point of contact with healthyocular tissue.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the invention to provide an ocularcutter having an outer needle and an inner needle with an enhancedcutting surface on the inner needle. It is further an object of theinvention to provide an ocular cutter where the inner needle is formedso that controlled, desired amounts of tissue are cut.

It is yet another object of the invention to provide an ocular cutterhaving an inner needle reciprocable within an outer needle such that theinner needle produces a precise cut between the outer needle and thetissue.

It is another object of the invention to provide an ocular cutter havingan inner needle reciprocable within an outer needle such that thedistance between the location of cutting and the contact point betweenouter needle and tissue is minimized.

It is finally an object of the invention to provide an ocular cutterhaving an inner needle reciprocable within an outer needle such that thelocation of cutting is moved closer to the point of contact betweeninner and outer needle of the cutter.

These and other objects of the invention are accomplished in an ocularcutter having an inner needle reciprocable within an outer needle.Within the outer needle there is a port into which tissue is pulled by asuction mechanism provided along the length of the inner needle. Theouter needle is swaged to a controlled inner diameter. The outerdiameter of the inner needle is oversized for the swaged inner diameterof the outer needle. Thus, the inner needle is placed within the outerneedle in an interference fit at the swaged area, but maintainsclearance over the remaining length of insertion within the outerneedle. Therefore, when the inner needle reciprocates within the outerneedle, there is a radial force, like a spring, on the inner needle atits point of contact with the outer needle. This causes a larger andmore accurate shear force on the tissue to be cut. Therefore, the tissueis more readily cut, with minimized adverse effects, such as tissuetrauma.

When the inner needle reciprocates within the outer needle, the outerneedle port is placed a minimum distance from the end of the outerneedle. In order to minimize the distance between the location of theport and the end of the outer needle, the inner needle is reciprocatedsuch that there is a positive stop made on the reciprocation of theinner needle. The inner needle is free to travel nearly the entirelength of the outer needle. Thus, the inner needle makes a sharp cutacross the entire outer needle port. Again, the tissue is more preciselycut. Because the outer needle port is positioned close to the end of theouter needle, the distance between the point of contact of the tissueand the port is reduced. Also, improvements are made to the drivemechanism of the cutter to respond to slightly misoriented parts or anyeccentricities in the drive shaft. This maximizes the usefulness ofcutting possible at the outer needle port, and makes the presentlyimproved ocular cutter more efficient for a varied number of uses.

These and other aspects of the invention will be better understood fromthe following figures and the detailed description which follow.

DETAILED DESCRIPTION OF THE DRAWINGS

The accompanying drawings will better describe the invention:

FIG. 1 is a perspective view of an ocular cutter of the invention;

FIG. 2 is an assembly drawing in cross-section of an ocular cutter ofthe invention;

FIG. 3 is an enlarged detail view of the ocular cutter of the inventionat the tip with the inner needle placed within the outer needle;

FIG. 4 is a cross-sectional view of the inner needle within the outerneedle at lines 4--4 of FIG. 3;

FIG. 5 is a view of the positive stop mechanism in the reciprocableshaft within the aspiration housing:

FIG. 6 is a perspective view of an end of the outer needle;

FIG. 7 is a cross-sectional view of an alternate embodiment of the camused in the invention; and

FIG. 8 is a graph of the motion of the cam in FIG. 7.

DETAILED DESCRIPTION OF THE INVENTION

As can be seen in FIGS. 1 and 2, the ocular cutter 10 of the presentinvention has inner needle 20 attached to a reciprocable shaft 25. Theinner needle 20 is generally hollow and shaft 25 contains an outlet 22for aspiration. Aspiration line 28 ensures suction of the displacedtissue away from the cutting site at the end of the needle. Shaft 25reciprocates within the aspiration sleeve 30, and includes eccentric end26. This end 26 interacts with spring loaded cam or wobble plate 50,which rotates. Upon rotation, the reciprocable shaft 25 is movedlongitudinally, due to the force from the cam or wobble plate 50 ontothe eccentric end 26 of the shaft. The inner needle 20 and reciprocableshaft 25 are generally forced away from the cutting site by means of thespring 24. Spring 24 overcomes the forces at the cutting site as well asthe force of the O-ring seal 27, which seals shaft 25 to the cutterhousing or aspiration sleeve 30.

Aspiration takes place at aspiration line 28 and through the hollowinner needle 20 via aspiration outlet 22 on reciprocable shaft 25.Aspiration sleeve 30 fits on handpiece 40 by means of the bayonet pin35, as seen in FIG. 2. In addition, flexible elastomer infusion sleeve60 fits over the collar 32 of the aspiration sleeve 30. The cylindricalbody 62 of infusion sleeve 60 seals around collar 32 of aspirationsleeve 30 in an interference fit. This allows the surgeon to adjust therelationship between infusion tip 90 and port 72, within aboutone-sixteenth inch. The infusion sleeve 60 provides the proper fluidflow within infusion tip 90 over the outer needle 70.

At the end of the infusion sleeve 60 is infusion tip 90 which fits overouter needle 70. The outer needle 70 fits over the inner needle 20 sothat the inner needle 20 is reciprocable within the outer needle 70.Outer needle 70 contains port 72, through which the tissue is aspirated.Tissue is pulled into port 72 by the vacuum created by an aspirationmechanism through hollow inner needle 20. When the inner needle 20reciprocates in the outer needle 70 by means of the wobble plate 50 andthe reciprocating shaft 25, the end of the inner needle 20 shears theocular tissue exposed within outer needle 70 through outer needle port72. The tissue has been infused with fluid from the infusion sleeve 60through infusion tip 90 and infusion port 92. Once the tissue issheared, it is aspirated out of the instrument via the aspiration sleeve28.

As can be further seen from FIGS. 3 and 4, the outer needle 70 is swagedat its end 71 slightly reducing the diameter of outer needle 70. Swagingcreates a more uniform inner diameter 73 and improves the surface finishof outer needle inner diameter 73. This creates a better interferencefit with inner needle 20, and improves cutting. Inner diameter 73 isalso slightly tapered toward its end, so that inner needle 20 may bereceived within outer needle 70. Strategically, inner needle 20 is sizedso that its outer diameter is larger than the inner diameter 73 of outerneedle 70 at the swaged end 71. There is clearance between inner needle20 and outer needle 70 over the remaining length of outer needle 70,back toward the aspiration sleeve 30.

When inner needle 20 is inserted into the outer needle 70 andreciprocates within the outer needle 70, inner needle end 21reciprocates within outer needle swaged end 71. Inner needle 20 isground at end 21 so that the circumference of inner needle 20 has an arcof about one quarter the circumference removed at end 21. A taperedrelief 21a is also provided on the external surface of inner needle end21 to create clearance within outer needle 70 all around inner needle20, except for the end 21 of inner needle 20.

When inner needle 21 reciprocates, there is an outward radial force fromthe inner needle end 21 on the outer needle inner diameter 73, based onthe deflection of the inner needle end 21 in order to create theinterference fit within the outer needle inner diameter 73. The outerradial force F causes the inner needle 20 to press more firmly againstthe inner diameter 73 of the outer needle 70. The tapered relief 21a ofouter needle end 21 is sufficiently large to create contact at onlyinner needle end 21 reciprocating within swaged outer needle end 71. Thepliability of tapered relief 21a insures deflection of end 21.

The enhanced inner needle 20, in combination with the outer needle 70,acts as a shear mechanism, like a scissors. Because the inner needle end21 experiences an outward force, it remains forced against the outerneedle 70, even though tissue to be cut is lodged in the inner needlepath as the inner needle 20 reciprocates. Therefore, the ocular tissueis sheared at its point of contact with the outer needle port 72. It hasbeen found that the force between needles 20, 70 is greater and moreuniform, because of the improved fit between needles 20, 70. The shearthat takes place at the outer needle port 72 is more stark and precise,resulting in a more accurate cutting motion created by the inner needle20.

Also, it is to be noticed in FIGS. 5 and 6 that reciprocating shaft 25is sized to be longer than the distance from the motorized cam 50 at itsmaximum stroke to the inner end 31 of aspiration sleeve 30. Therefore,as the cam 50 begins to rotate, the shaft 25 meets a positive stop atthe end 31 of aspiration sleeve 30. This positive stop is put to use atthe end of the two needles 20, 70. The inner needle 20 is configured sothat the distance between the inner needle end 21 and the outer needleend 71 is minimized. The outer needle port 72 is placed as close as canbe manufactured to the outer needle end 71. Because it is now easy tomanufacture inner needle 20 to reach the inside of outer needle end 71,it is certain that the inner needle 20 will cut all the tissue whichremains in the outer needle port 72 when the inner needle 20reciprocates across outer needle port 72. Because the outer needle port72 is placed close to the end 71 of the outer needle 70, the actual sitefor cutting ocular tissue is made very close to the outer needle end 71.Thus, greater accuracy is obtained in the positioning of the outerneedle 70 at the tissue which is to be cut. Tolerances for the marginbetween the outer needle end 71 and the tissue contacting the outerneedle end 71 are reduced. The present ocular cutter therefore operateswith more utility and can perform a wider variety of procedures.

Alternately, as seen in FIG. 7, cam 150 may be used in place of cam 50.This cam has a longitudinal displacement L, as seen in FIG. 8.Essentially cam 150 is machined so that there is an approximately 15° to30° dwell D. Also, cam 150 has a central bore 152, around which ismachined positional edge 154, for interaction with eccentric end 26 ofshaft 25. Positional edge 154, in profile, is machined so that at anyangular position A along cam 150, positional edge 154 will displaceeccentric end 26 longitudinally by the same amount regardless of radiallocation of eccentric end 26. Thus, tolerances on the position ofeccentric end are negated by uniformity of positional edge 154. Also,the dwell D seen in FIG. 8 functions such that when cam 150 is orientedat no stroke, cam 150 accommodates variations in angular position A ofeccentric end 26 up to 30° without any longitudinal displacement.

It is to be understood that the invention has been disclosed in relationto a particularly preferred embodiment, but that the invention is to bederived from the appended claims and their equivalents.

What is claimed is:
 1. A tissue cutter comprising:a hollow inner needlewith an elongated end and circular cross-section; and an outer needlewith circular cross-section enclosing an open inner portion, said outerneedle closed at one end, and said outer needle circular cross-sectioncontaining an opening near said one end for the insertion of tissue;said inner needle reciprocable within the inner portion of said outerneedle; and a rotary can means wherein said inner needle reciprocates bymotion against said cam means having a dwell at the end of the stroke ofsaid inner needle within said outer needle, said dwell extending atleast 15 degrees of angular rotation of said rotary cam means; whereinthe outer circumference of said inner needle is generally smaller thanthe inner circumference of said outer needle; and wherein the outercircumference of said elongated end gradually increases distally alongsaid inner needle length; such that at said elongated end, the outercircumference of said inner needle: (a) fits within the innercircumference of said outer needle in an interference fit; and (b) hasan arc greater than 120° along it circular cross-section removed.
 2. Thetissue cutter of claim 1 wherein said inner needle reciprocates with apositive stop at the end of said inner needle reciprocation within saidouter needle.
 3. The tissue cutter of claim 2 wherein said positive stopis effectuated at a drive shaft attached to said inner needle such thatsaid drive shaft abuts said outer needle at the end of said inner needlereciprocation, thereby preventing said inner needle from furtherentering said outer needle.
 4. The tissue cutter of claim 1 wherein saidouter needle end is swaged.
 5. The tissue cutter of claim 4 wherein saidremoved arc forms a partial cylinder along the elongated end of saidinner needle.
 6. The cutter of claim 5 wherein said outer needle istaper toward said outer needle end to enhance the interference fit withsaid inner needle.
 7. The cutter of claim 5 wherein said drive shaftabuts the end of said outer needle in a positive stop at the end of thestroke of said inner needle.
 8. The cutter of claim 1 wherein said outerneedle is tapered toward said outer needle end to enhance theinterference fit with said inner needle.